In a touch panel, an input device having a conductive substrate, in which a transparent conductive layer (transparent conductive film) is formed on the surface of a transparent insulating substrate, is provided as an electrode sheet in the front surface of an image display device such as a liquid crystal display.
As a material that constitutes the transparent conductive layer in the conductive substrate of an input device, tin-doped indium oxide (ITO) or π-conjugated conductive polymers (organic conductors) represented by polyethylenedioxythiophene/polystyrene sulfonate are widely known.
Incidentally, in the conductive substrate used in an input device for touch panels, a circuit pattern or an antenna array pattern is formed at times.
In terms of the method for forming patterns, for example, in Patent Document 1, a method has been disclosed, in which a transparent conductive layer is formed all over the surface of a transparent base material by coating, followed by removal of the transparent conductive layer at a portion to be insulated through ablation by irradiating a CO2 laser beam or a YAG laser beam that uses a Q switch and having a pulse width of about 100 nanoseconds.
In Patent Documents 2 and 3, methods for forming a conductive portion with a predetermined pattern on the surface of a transparent base material by a printing method such as a screen printing method and a gravure printing method have been disclosed.
In Patent Document 4, a method has been disclosed, in which a transparent conductive layer is formed all over the surface of a transparent base material by coating, followed by removal of the transparent conductive layer at a portion to be insulated by plasma etching.
In Patent Document 5, a technique for forming a conductive pattern has been disclosed, in which a laser beam is irradiated for insulation onto a transparent conductive film that is made by dispersing and hardening a metal nanowire (metal microfiber) in a binder (resin). Note that the metal nanowire projected outside the transparent conductive film is removed by laser.
In Patent Document 6, a technique for forming a fine pattern, by means of fine ablation of the order of about 10 μm, by using an ultraviolet laser with respect to an ITO deposited substrate for touch panels, controlling the focal length between the beam diameter and the lens, and controlling the processing width within a light condensing area.